diff --git a/sources/tech/20210101 Resize images using Python.md b/sources/tech/20210101 Resize images using Python.md new file mode 100644 index 0000000000..10e3d6850c --- /dev/null +++ b/sources/tech/20210101 Resize images using Python.md @@ -0,0 +1,83 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Resize images using Python) +[#]: via: (https://opensource.com/life/15/2/resize-images-python) +[#]: author: (Dayo Ntwari https://opensource.com/users/dayontwari) + +Resize images using Python +====== +A quick explanation of how to resize images in Python while keeping the +same aspect ratio. +![Python in a tree][1] + +I love [Python][2], and I've been learning it for a while now. Some time ago, I wrote a Python script where I needed to resize a bunch of images while at the same time keeping the aspect ratio (the proportions) intact. So I looked around and found [Pillow][3], a Python imaging library and "friendly fork" of an old library just called PIL.  + +To install Pillow, use the `pip` module of Python: + + +``` +`$ python3 -m pip install Pillow` +``` + +### Scaling by width + +Here's a basic script to resize an image using the Pillow module: + + +``` +from PIL import Image + +basewidth = 300 +img = Image.open('fullsized_image.jpg') +wpercent = (basewidth / float(img.size[0])) +hsize = int((float(img.size[1]) * float(wpercent))) +img = img.resize((basewidth, hsize), Image.ANTIALIAS) +img.save('resized_image.jpg') +``` + +These few lines of Python code resize an image (**fullsized_image.jpg**) using Pillow to a width of 300 pixels, which is set in the variable **basewidth** and a height proportional to the new width. The proportional height is calculated by determining what percentage 300 pixels is of the original width (**img.size[0]**) and then multiplying the original height (**img.size[1]**) by that percentage. The resulting height value is saved in the variable **hsize.** + +You can change **basewidth** to any other number if you need a different width for your images. Also, notice I saved the resized image under a different name, **resized_image.jpg**, because I wanted to preserve the full-size image (**fullsized_image.jpg**) as well. You don't have to do this, of course. You can use the same filename to overwrite the full-size image with the resized image, if that is what you want. + +### Scaling by height + +If the height is fixed and the width proportionally variable, it's pretty much the same thing, you just need to switch things around a bit: + + +``` +from PIL import Image + +baseheight = 560 +img = Image.open('fullsized_image.jpg') +hpercent = (baseheight / float(img.size[1])) +wsize = int((float(img.size[0]) * float(hpercent))) +img = img.resize((wsize, baseheight), Image.ANTIALIAS) +img.save('resized_image.jpg') +``` + +Notice **basewidth** is now **baseheight**, since height is fixed. In the third line, we are calculating the height percentage, so we need **img.size[1]** instead of **img.size[0]**. The size attribute is a tuple containing width and height in pixels; **size[0]** refers to the first tuple element, which is the width, and **size[1]** is the second element, which is height. Line 4 also has this switch between **size[0]** for width and **size[1]** for height. + +_Originally published on Dayo Ntwari's [blog][4] and republished under Creative Commons with permission._ + +_This article was updated in January 2021 by the editor._ + +-------------------------------------------------------------------------------- + +via: https://opensource.com/life/15/2/resize-images-python + +作者:[Dayo Ntwari][a] +选题:[lujun9972][b] +译者:[译者ID](https://github.com/译者ID) +校对:[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/dayontwari +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/life-python.jpg?itok=F2PYP2wT (Python in a tree) +[2]: http://python.org/ (Python Programming Language – Official Website) +[3]: https://pypi.org/project/Pillow/ (Python Imaging Library) +[4]: https://dayontwari.wordpress.com/2015/01/06/how-to-resize-images-with-python/